This is Your Brain on Stress. Any Questions?

I really enjoyed this Seed article on neurogenesis. Much of this points the way to the kind of thing a scientifically credible study of happiness would involve (i.e., not extrapolations from silly surveyrs, but things like the way stress impedes neural regeneration). Of course, even a bit of significant plasticity raises interesting social questions. Or, as the author of the article puts it:

The social implications of this research are staggering. If boring environments, stressful noises, and the primate’s particular slot in the dominance hierarchy all shape the architecture of the brain—and Gould’s team has shown that they do—then the playing field isn’t level. Poverty and stress aren’t just an idea: they are an anatomy. Some brains never even have a chance.

This seems to me to be a paragraph that isn’t thought through. First, the social implications we’re interested in are human social implications, not marmoset social implications. But primates all, yes. Now, the fact that there is a dominance hierarchy at all says that the playing field isn’t level. The fact that the brains of the alpha and omega are different isn’t a side-effect of their positions in the hierarchy. It’s part of what the hierarchy is. And then poverty comes out of absolutely nowhere at this point of the article. Who thought poverty was an idea? And we’ve known stress is a physical condition for a long time. What’s going on!?

We get some explanation later on:

Subsequent experiments have teased out a host of other ways stress can damage the developing brain. For example, if a pregnant rhesus monkey is forced to endure stressful conditions—like being startled by a blaring horn for 10 minutes a day—her children are born with reduced neurogenesis, even if they never actually experience stress once born. This pre-natal trauma, just like trauma endured in infancy, has life-long implications. The offspring of monkeys stressed during pregnancy have smaller hippocampi, suffer from elevated levels of glucocorticoids and display all the classical symptoms of anxiety. Being low in a dominance hierarchy also suppresses neurogenesis. So does living in a bare environment. As a general rule of thumb, a rough life—especially a rough start to life—strongly correlates with lower levels of fresh cells.

Gould’s research inevitably conjures up comparisons to societal problems. And while Gould, like all rigorous bench scientists, prefers to focus on the strictly scientific aspects of her data—she is wary of having it twisted for political purposes—she is also acutely aware of the potential implications of her research.

“Poverty is stress,” she says, with more than a little passion in her voice. “One thing that always strikes me is that when you ask Americans why the poor are poor, they always say it’s because they don’t work hard enough, or don’t want to do better. They act like poverty is a character issue.”

Gould’s work implies that the symptoms of poverty are not simply states of mind; they actually warp the mind. Because neurons are designed to reflect their circumstances, not to rise above them, the monotonous stress of living in a slum literally limits the brain.

So, ah! Here’s the politics. And here’s where the brilliant Gould gets pretty confused. Why think character issues have nothing to do with, say, neurogenesis? Aristotle says virtue is a hexis, a habit, a settled disposition of the soul to feel and act. Losing neurons, or failing to repair neurons, that are implicated in hedonic tone and motivation surely has something to with habit, virtue, character. No?

Here’s a conjecture. I think the “potentional implications” here are mostly socially conservative. It’s true that not having enough can be stressful. But most Americans in “poverty” have enough. So here’s where folks on the left want to shift the question to the dominance hierarchy. (That’s ostensibly what that Cassidy article was about.) Low status: now that’s stressful. The question mark after “steal underpants” and before “profit” here is some mysterious mapping of a primate dominance hierarchy on to a local or even national income scale. But what matters primate-wise is the very local band or troop. The low status rhesus isn’t stressed out by the high status rhesus the next forest over. He’s tyrranized by his second cousin. So, if we’re talking about the stressors of poverty, we have to ask, What accounts for high and low status in low income communities? If the answer is not something the aspiration to which is likely to precipitate a climb from poverty (i.e., hard work, team spirit, punctuality), then think about that. I’m not going to go all Bill Cosby on you, but I think you can see where this can go. Note also that in many poor neighborhoods and communities, the family, if there is a family, is more or less chaotic—lacking order, clear moral expectations, and the background assurance of responsible loving care. That’s surely stressful. But it is not the poverty per se that is doing it. It is the culture. Amish folk living peacefully under the poverty line are not losing neurons in droves to the stress of their modest economic status. And I bet some of the kids out there soaked in glucocorticoids have pretty nice cell phones.

I look forward with eager anticipation to the social neuroscience of the very near future, when Odling-Smee niche construction theory and Boyd-Richerson cultural evolution theory meet neurogenesis. In human environments, status is culturally shaped, and so status-related stress and neural damage are too culturally shaped. If we find out that status competition in some cultures leads to large overall gains, and pretty small negative effects, while status competition in other cultures leads to stress-induced brain warp, then . . . well, we’ll really know something, won’t we?

Author: Will Wilkinson

Vice President for Research at the Niskanen Center